1. Field of the Invention
The present invention relates to a positive-resist composition, especially to a chemically amplified positive-resist composition, suitable as a micropatterning material, especially for the VLSI manufacture, or for manufacture of a photomask pattern, which shows a high alkali dissolution-rate contrast before and after exposure, high sensitivity and high resolution, a reduced line edge roughness, and an outstanding etching resistance in exposure with a high energy beam.
2. Description of the Related Art
In recent years, with a tendency that integration and speed have become higher in LSI, a tendency that a pattern rule becomes finer progresses rapidly. In the background that the tendency that a pattern becomes finer has progressed quickly, there are a tendency that NA of a projection lens has become higher, improvement in resist performance, and a tendency that a wavelength has become shorter. Especially a tendency that a wavelength becomes shorter from i line (365 nm) to KrF (248 nm) causes a big change, and thus mass production of a device with 0.18 μm rule is also made possible. The chemically amplified positive-resist composition in which an acid is used as a catalyst (for example, see Japanese Patent Publication No. 2-27660 and Japanese Patent Application Laid-open (KOKAI) No. 63-27829) has an outstanding feature in the tendency that resolution and sensitivity of resist become higher, and thus has become a main resist composition especially for deep-ultraviolet lithography.
The resist composition for KrF excimer lasers has began to be used generally for a 0.3-micron process, and it has also been began to be applied to mass-production of 0.18-micron rule via a 0.25-micron rule. Furthermore, examination of a 0.15 micron rule has also been started, and the tendency that a pattern becomes finer is accelerated increasingly. It is expected that a design rule should be 0.13 μm or less with a tendency that a wavelength becomes shorter from a KrF excimer laser to an ArF excimer laser (193 nm). However, it was hard to use novolak and polyvinyl phenol resin which have been used conventionally as a base resin for resist, since it has a quite strong absorption near the wavelength of 193 nm. Then, aliphatic resins such as acrylic resins or cycloolefin resins have been examined to ensure transparency and a required dry etching resistance (for example, see Japanese Patent Application Laid-open (KOKAI) No. 9-73173, Japanese Patent Application Laid-open (KOKAI) No. 10-10739, Japanese Patent Application Laid-open (KOKAI) No. 9-230595, and International publication No. 97/33198).
Among them, the resist based on (meth)acrylic base resin with a high resolution has been examined. As (meth)acrylic resin, the combination of the (meth)acrylic which has methyl adamantane ester as an acid labile group unit and the (meth)acrylic which has an ester of a lactone ring as an adhesion group unit has been proposed (for example, see Japanese Patent Application Laid-open (KOKAI) No. 9-90637). Furthermore, norbornyl lactone has been proposed as an adhesion group by which an etching resistance is reinforced (for example, see Japanese Patent Application Laid-open (KOKAI) No. 2000-26446 and Japanese Patent Application Laid-open (KOKAI) No. 2000-159758).
Reduction of line edge roughness and reduction of residue after development are mentioned as one of the problems in ArF lithography. Swelling at the time of development is mentioned as one of the causes for line edge roughness. Although polyhydroxy styrene used as a resist for KrF lithography is hardly swelled since phenol thereof is a weakly acidic group and has a moderate alkali solubility, swelling at the time of development is easily caused in the polymer containing a highly hydrophobic alicyclic group, since it is dissolved with a carboxylic acid with high acidity.
Here, the amount of swelling during development has been reported by measurement of the development characteristics of the resist according to the QCM (Quartz Crystal Microbalance) method (for example, see Proc. SPIE Vol. 3999 p2 (2000)). Although swelling of the film during development cannot be observed by a conventional optical interference thickness-measurement method, it is possible to observe increase in weight of the film by swelling according to the QCM method, since the weight change of a film is measured electrically. In the reference, swelling of the ArF resist based on cycloolefin polymer is disclosed. Significant swelling is observed especially in the case that a carboxylic acid is used as an adhesion group.